标题: An Expert Panel Calls for Upgrading Earthquake Warning System in Calif [打印本页] 作者: choi 时间: 1-29-2013 11:43 标题: An Expert Panel Calls for Upgrading Earthquake Warning System in Calif Rong-Gong Lin II and Rosanna Xia, Quake experts call for an advance-warning system for California
A proposed $80-million system similar to one in Japan would use sensors in the ground to alert residents before a temblor strikes and would be the first such network in the U.S. Los Angeles Times, Jan 29, 2013. http://www.latimes.com/news/loca ... ke-warning-20130129,0,5545398.story
Quote:
"In the devastating 2011 Japan earthquake, a sensor embedded in the ground detected the first signs of movement and immediately sent out an alert at the speed of light. Within seconds, text messages warning of impending shaking went out to roughly 50 million people.
"Many people in Tokyo, 200 miles away from the epicenter, knew the quake was coming before they felt the shaking about 30 seconds later. Trains were able to slow down or stop, and not a single car derailed.
(b) "The US is behind Japan as well as Mexico, Taiwan, Turkey and even Romania in creating early alert systems. Last year, residents in Mexico City were warned shortly before the shaking from a 7.4 quake that began near Acapulco arrived.
Note:
(a) The summary of the report: California "State Sen Alex Padilla (D-Pacoima) is proposing legislation to create the statewide network. California already has hundreds of ground sensors measuring earth movement, but experts said another $80 million is needed to expand and upgrade the monitors."
Naturally California legislature may or may not pass the bill.
(i) The Spanish surname Padilla is from a few place names of the same spelling--"named from Spanish [noun] padilla ‘frying pan’, ‘breadpan’ (Latin patella, a diminutive of patina ‘shallow dish’), a word which was commonly used in the topographical sense of a gentle depression.
(ii) The patella is the Latin medical term ("kneecap" in English; 膝蓋骨 in Taiwan).
(b)
(i) earthquake warning system http://en.wikipedia.org/wiki/Earthquake_warning_system
(c) P wave http://en.wikipedia.org/wiki/P-wave
("The name P-wave is often said to stand either for primary wave, as it has the highest velocity and is therefore the first to be recorded; or pressure wave, as it is formed from alternating compressions and rarefactions"/ longitudinal wave; section 2.2 As an earthquake warning)
* longitudinal wave http://en.wikipedia.org/wiki/Longitudinal_wave
(section 1 Non-electromagnetic: sound wave and seismic P wave; section 2 Electromagnetic: "Maxwell's equations lead to the prediction of electromagnetic waves in a vacuum, which are transverse * * * However, [electromagnetic] waves can exist in plasmas or confined spaces, called plasma waves, which can be longitudinal, transverse, or a mixture of both")
S wave is a "transverse wave, so motion is perpendicular to the direction of wave propagation: S-waves are like waves in a rope, as opposed to waves moving through a slinky, the P-wave.
"Its name, S for secondary, comes from the fact that it is the second direct arrival on an earthquake seismogram, after the compressional primary wave, or P-wave, because S-waves travel slower in rock.
(e) You do not understand longitudinal and transverse waves? No problem.
UPSeis; An educational site for budding seismologists. Michigan Technology University (MTU), undated. http://www.geo.mtu.edu/UPSeis/waves.html
(body Waves: P wave and S wave)
Quote:
(i) P wave: "It pushes and pulls the rock it moves through just like sound waves push and pull the air. Have you ever heard a big clap of thunder and heard the windows rattle at the same time? The windows rattle because the sound waves were pushing and pulling on the window glass much like P waves push and pull on rock.
(ii) S wave: "S waves move rock particles up and down, or side-to-side--perpindicular to the direction that the wave is traveling in (the direction of wave propagation).